I've searched the tutorials all day. My eyes are bleeding. Can't find the answer! (lol)

I'm able to change the colors for background, fonts, etc in my classic theme, but I canNOT find a way to change the Green Box color of the sidebox things. Like Documents/Categories/ Featured Products

I've edited the other stuff but cannot for the life of me find where the code is at in the stylesheet to change these stinking boxes

Any help would be a godsend. Thanks!